LH and FSH - What They Measure and Why They Are Tracked

Understanding LH and FSH

LH and FSH are two hormones released by the pituitary gland. They are commonly reviewed together on a hormone panel because they sit on the pituitary side of the reproductive hormone axis, above the sex hormones such as testosterone. This page explains, in plain language, what LH and FSH are, why they are commonly measured, and how they add signaling context alongside the testosterone markers.

Everything here is educational context. It does not interpret what any particular value means, does not diagnose, and does not describe any course of action.

What LH and FSH are

• LH stands for luteinizing hormone.
• FSH stands for follicle-stimulating hormone.
• Both are produced by the pituitary gland at the base of the brain.
• They are part of reproductive hormone signaling and are released in response to gonadotropin-releasing hormone (GnRH) from the hypothalamus.
• They are commonly reviewed alongside sex hormone markers such as testosterone, because they act on the gonads.

In the male reproductive axis, LH acts on the Leydig cells of the testes, which produce testosterone, while FSH acts on the Sertoli cells. In the female reproductive axis, LH and FSH act on the ovaries and vary across the menstrual cycle. Because they are pituitary signals, LH and FSH describe the "upstream" side of the axis rather than the sex hormones themselves.

Why LH and FSH are commonly measured

LH and FSH are commonly measured as part of a broader look at the reproductive hormone axis, usually together with testosterone-related markers. In research and clinical education they add context in several ways:

• Hormone panels — LH and FSH are routine companions when sex hormones are ordered.
• Reproductive-axis context — they describe activity on the pituitary side of the axis.
• Pituitary-gonadal signaling — they are the signals the pituitary sends toward the gonads.
• Testosterone context — because LH signals the testes to produce testosterone, it is read alongside the testosterone markers.
• Age and sex context — LH and FSH differ by sex and change across life stages, so they are read within the context of the individual.

This page does not interpret what any particular value means and does not recommend any action. Any individual measurement should be discussed with a licensed healthcare provider.

Relationship to testosterone biomarkers

LH and FSH are most useful when read alongside the sex hormone markers, because together they describe different points along the hormone axis:

• Total Testosterone measures the combined amount — both bound and unbound testosterone.
• Free Testosterone measures only the unbound fraction.
• SHBG helps explain the binding context between total and free testosterone.
• LH and FSH provide pituitary-gonadal signaling context from the pituitary side of the axis.
• DHEA-S provides adrenal androgen-related context.

For a broader view of how these markers fit together, see the Testosterone Overview.

Common units

LH and FSH are most often reported in IU/L (international units per liter), sometimes written as mIU/mL (milli-international units per milliliter), which is the numerically equivalent unit. Units and assay methods vary by laboratory, so always read the unit printed next to your own measurement.

Public reference example

The figures below are a public reference example drawn from a published source and labeled by the study population they came from. They are shown for educational context only.

Reference ranges vary by laboratory, assay, age, sex, menstrual-cycle phase where relevant, and population. This is a public reference example for education, not a universal standard and not a determination about any individual. Where a measurement is available, Pepvela prioritizes the reference range printed on your own lab report.

Age and sex context

LH and FSH reference intervals differ by sex, and they also change with age, pubertal stage, and — in females — menstrual-cycle phase and menopausal status. A figure drawn from one sex, life stage, or cycle phase may not correspond to another.

For this reason, LH and FSH are read within the reference interval that matches the individual, the life stage, and the specific laboratory performing the measurement, rather than against a single fixed number.

Related biomarkers

These related biomarkers are often reviewed alongside LH and FSH for educational context:

Related peptide research

Research literature involving certain compounds may measure reproductive hormone or hormone-axis markers as endpoints. The following research pages are provided for educational context only and make no claim about any effect on LH, FSH, or testosterone:

Citations

1. MedlinePlus. Luteinizing Hormone (LH) Levels Test. U.S. National Library of Medicine. https://medlineplus.gov/lab-tests/luteinizing-hormone-lh-levels-test/
2. MedlinePlus. Follicle-Stimulating Hormone (FSH) Levels Test. U.S. National Library of Medicine. https://medlineplus.gov/lab-tests/follicle-stimulating-hormone-fsh-levels-test/
3. Nedresky D, Singh G. Physiology, Luteinizing Hormone. StatPearls. NCBI Bookshelf. https://www.ncbi.nlm.nih.gov/books/NBK539692/
4. Orlowski M, Sarao MS. Physiology, Follicle Stimulating Hormone. StatPearls. NCBI Bookshelf. https://www.ncbi.nlm.nih.gov/books/NBK535442/
5. Winters SJ. Laboratory Assessment of Testicular Function. Endotext. NCBI Bookshelf. https://www.ncbi.nlm.nih.gov/books/NBK279145/